Even if you
drink diet soda -- instead of the sugar variety -- you could still have
a much higher risk of vascular events compared to those who don't drink
soda, according to research presented at the American Stroke
Association's International Stroke Conference 2011.

In findings involving 2,564 people in the
large, multi-ethnic Northern Manhattan Study (NOMAS), scientists said
people who drank diet soda every day had a 61 percent higher risk of
vascular events than those who reported no soda drinking.

"If our results are confirmed with future
studies, then it would suggest that diet soda may not be the optimal
substitute for sugar-sweetened beverages for protection against
vascular outcomes," said Hannah Gardener, Sc.D., lead author and
epidemiologist at the University of Miami Miller School of Medicine in
Miami, Fla.

In separate research using 2,657
participants also in the Manhattan study, scientists found that high
salt intake, independent of the hypertension it causes, was linked to a
dramatically increased risk of ischemic strokes (when a blood vessel
blockage cuts off blood flow to the brain).

In the study, people who consumed more than
4,000 milligrams (mg) per day of sodium had more than double the risk
of stroke compared to those consuming less than 1,500 mg per day.

At the start of both studies, researchers
assessed diet by a food frequency questionnaire.

NOMAS is a collaboration of investigators at
Columbia University in New York and Miami's Miller School of Medicine,
launched in 1993 to examine stroke incidence and risk factors in a
multi-ethnic urban population. A total of 3,298 participants over 40
years old (average age 69) were enrolled through 2001 and continue to
be followed. Sixty-three percent were women, 21percent were white, 24
percent black and 53 percent Hispanic.

In the soda study, researchers asked
subjects at the outset to report how much and what kind of soda they
drank. Based on the data, they grouped participants into seven
consumption categories: no soda (meaning less than one soda of any kind
per month); moderate regular soda only (between one per month and six
per week), daily regular soda (at least one per day); moderate diet
soda only; daily diet soda only; and two groups of people who drink
both types: moderate diet and any regular, and daily diet with any
regular.

During an average follow-up of 9.3 years,
559 vascular events occurred (including ischemic and hemorrhagic
stroke, which is caused by rupture of a weakened blood vessel).
Researchers accounted for participants' age, sex, race or ethnicity,
smoking status, exercise, alcohol consumption and daily caloric intake.
And even after researchers also accounted for patients' metabolic
syndrome, peripheral vascular disease and heart disease history, the
increased risk persisted at a rate 48 percent higher.

Only a third of participants met the current
U.S. Dietary Guidelines for Americans that recommend daily sodium
intake fall below 2,300 mg, or about a teaspoon of salt, Gardener said.
Only 12 percent of subjects met the American Heart Association's
recommendations to consume less than 1,500 mg a day. Average intake was
3,031 milligrams.

"The take-home message is that high sodium
intake is a risk factor for ischemic stroke among people with
hypertension as well as among those without hypertension, underscoring
the importance of limiting consumption of high sodium foods for stroke
prevention," Gardener said.

Participants' reporting their dietary
behavior is a key limitation of both studies, Gardener said.

In the soda study, investigators also lacked
data on types of diet and regular drinks consumed, preventing analysis
of whether variations among brands or changes over time in coloring and
sweeteners might have played a role.